1. Field of the Invention
This invention is directed to a method to improve the superconducting transition temperature of the YBa.sub.2 Cu.sub.3 O.sub.6 to 7 ceramic.
2. Brief Description of the Prior Art
Traditionally the YBa.sub.2 Cu.sub.3 O.sub.6 to 7 superconductor is made by well known ceramic processing methods. These methods Include starting by mixing and grinding powders of yttrium oxide, barium carbonate and copper oxide. This mixture, after thorough grinding, is heat treated or calcined at temperatures between about 800.degree. C. to about 1050.degree. C. in order to drive the carbonate from the mixture. The powders, after ball milling and mixing a second time, are sintered to densify and join the powders at temperatures from about 800.degree. C. to about 1050.degree. C. The powders are then annealed after sintering in oxygen or air at about 400.degree. C. to about 600.degree. C. to be sure the oxygen atoms in each molecule of YBa.sub.2 Cu.sub.3 O.sub.6 + is between 6 to 7 oxygen atoms. The prior art teaches that by adding silver oxide to the powder mixtures it is possible to increase the onset of the superconducting transition temperature to as high as 95K from the more usual 88K to about 90K. Unfortunately, the density and quality was not as required for use.
The density and quality of the finished product, particularly when the superconductor is to be a reliable wire, electrical device or other product made with this material, is of upmost importance. This invention yields a reliable superconductor product as set out below, and in particular improves the superconducting transition temperature of the YBa.sub.2 Cu.sub.3 O.sub.6 to 7.